Mercury switch



July 24, 1934. C,l H LARSQN 1,967,247

MERCURY SWITCH Filed July 21, 1953 fill/1:11111.

Patented July 24, 1934 PATENT OFFICE 1,967,247 MERCURY SWITCH Carl H. Larson, Elkhart, I-nd., assignor to The Adlake Company,V a corporation of Illinois Application July 21, 1933, Serial No. 681,408

` 16 Claims. (Cl. 2'00-112) The principal object of this invention is to provide aheavy duty mercury switch capable of withstanding the destructive effects of high amperage loads. f

Further and other objects and advantages will become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawing, in which Fig. 1 illustrates a front contact switch embodying the features of this invention, the switch .being shown in de-energizcd position;

` Fig. 2 is a View showing the same switch in energized position;

Fig. 3 is a plan view of the switch;

Fig. 4 is a perspective view of the displacer with the springs removed;

Fig. 5 illustrates ah modied construction of the plunger;

Fig. 6 is a sectional view showing a time delay frontcontact switch embodying the principles of this invention;

Fig.v 7 shows the switch of Fig. 6 in energized position; and

Fig. 8 illustrates a circuit in which the switch of this invention may-be advantageously employed.

The sparking which occurs in a circuit breaker of any kind depends to a large extent upon the load which the circuit breaker carries. If the load consists of a battery of lamps, there is likely to be considerable sparking when the circuit is being closed due to the initial surge in the circuit. If the circuit breaker carries an inductance load` such as a motor or transformer, there will be a tendency for an arc to form across the ,contacts when the circuit is being broken because of the inductance in the circuit. Other kinds `of loads will produce other characteristic effects.

The present invention takes into account the effect which various .kinds of l'oad have upon the arcing tendencies of a circuit breaker and provides a switch construction that can stand up over a long period of time under these severe and destructive conditions.

-Tests have shownthat a switch constructed in accordance with this invention will last ten times as long as a similar switch not embodying the improvements of this invention under an inductive load` at 110 volts A. C. and 2 amperes.

Itwill be understood that the illustration and vdescription of preferred forms of the invention are for the purpose of disclosureonly and are not .to be interpreted as imposing limitations upon the appended claims except as required by the prior art.

Referring now to the drawing, and particularly to Figs. 1 and 2, the reference character 10 designates a coil which consists of a spool 11 over which a suitable number of turns of copper wire 12 are wound. The spool has a" square central 30 opening 13 that isadapted to receive an iron yoke 14 which passes through the coil and has radially extending arms 15 and 16 positioned one above the other. The ends of the arms are rounded as shown at 17 in Fig. 3 to conform to the 05 peripheries of the iron pole sleeves .18 and 19 which are held against the yoke by clips 20 secured to the arms 15 and 16 by nuts and bolts 21 or equivalent means'. The pole sleeves are preferably made of Swedish iron and are adjustable within the clips 20 so that the air gap 22 between vtheir inner ends may be suitably located. Preferably the pole sleeves are provided with a slit 23 in order` to prevent eddy currents from travel- 4 ling around the sleeve when the relay is operating on alternating current.

'Ihe yoke and pole sleeves for convenience may be called the iron or magnetic circuit of the relay, and it will be noticed that this circuit is closed except for the single air gap 22.

The iron circuit supports a mercury switch 24 which comprises a glass envelope 25 through the base of which electrodes 26 and 27 areA pinchsealed. The central electrode 26 is substantially on the axis of the envelope and is surrounded by a glass insulating sleeve 28 which extends from the pinch seal 29 to a point 30 slightly below the top of the electrode. The bared portion 31 of the electrode 26 is bent over to one side as shown in the drawing, with the portion 32 ex- 90 tending below the top 30 of the insulating sleeve 28.

The switch envelope is preferably made of glass having'a high melting point and a low coefficient of thermal expansion, such for example as the glass specified in Weintraub Patent No. 1,154,081. It is also preferred that the glass should be substantially free-from compounds of lead,'tin, antimony, and other substances which are decomposed by the action of an electric arc.

The electrodes 26 and 27 may be made of tungsten, molybdenum, tantalum, or any other electrode material having suitable properties of expansion and fusibility with the particular glass used in the envelope.

A quantity of purified mercury 33 is placed in the, envelope during the process of manufacture and the amount is such that when thedisplacer or plunger, generally designated 34, is in the position shown in Fig. 1, the mercury level will be below the depending portion 32 of the electrode 26.

Prior to sealing 01T the top of the switch, as shown at 35, the envelope is thoroughly evacuated, and a suitable gas ll is introduced. The gas lill may be helium, hydrogen, a physical mixture of helium and hydrogen, helium hydride, or any other suitable gas ll known to the art.

The' switch envelope is held in proper positionl loosely within the outer sleeve and projects at both ends beyond the latter sleeve. The two sleeves 'are held in fixed relation by helical springs 39 and 40 which t tightly over the projecting ends of the sleeve 38 and abut the ends ofthe sleeve 37. Portions of the springs 39 and 40 extend beyond the ends of the sleeve 38 so that they .not only serve to hold the sleeves in xed relation, but also act as cushions for the plunger in its vertical movement within the switch envelope.

The plunger 34 is guided in its movement within the envelope by lugs 41 which are formed on the outer sleeve 37. The sleeve is also preferably provided with a longitudinal slit 42 for the same reason that the pole sleeves are similarly slitted.

' `It will be understood that the plunger being partly composed of magnetic material responds to the energization of the coil 10 by moving downwardly to the position shown in Fig. 2 to close the air gap 22. This downward movement causes a displacement of mercury which brings the mercury level above the depending portion 32 'of the central electrode and establishes an electrical connection between the central electrode and the electrode 27, the latter being constantly in contact with the mercury. When the coil is de-energized, the plunger rises to the position shown in Fig. 1 and the electrical circuit through the electrodes 26 and 27 is again broken.

It has been found by experiment that when the bared portion 31 of the electrode is not bent over in the manner whichhas been described, but is vertical, there is a tendency for the top portion of the glass insulating sleeve 28 to disintegrate when the arcing between the electrode 26 and the mercury becomes severe under high This is particularly true when amperage loads. the switch is used in a circuit such as shown in Fig. 8 in which the switch carries a high inductive load.

The-circuit shown in Fig. 8 is one which illustrates a thermostatic control for a motor, the control circuit being shown at 43 and the motor circuit at 44. Both circuits are energized from a "power line 45 which may be 110 volts alternating current. The control circuit 43 operates on reduced voltage and includes a thermostatic switch 46, relay coil 47, and the secondary coil 48 of a step-down transformer 49. The motor -circuit 44 includes theswitch 24 and motor 50.

When the bared portion 31 of the electrode 26 is bent to one side so that a portion extends below the top of the insulating sleeve 28, the insulating sleeve 28 is protected from disintegrating as the arc occurs directly between the mercury and the depending portion 32 of the electrode.

The plunger construction also as sists in enabling the switch to withstand high amperage loads. The refractory material of which the inner sleeve 38 is made protects the magnetic sleeve 37 from the ravages of the electric arc and prevents the release of occluded gases from the magnetic sleeve. Since the refractory sleeve 38 fits loosely within the magnetic sleeve, there is poor heat conduction between the two, and this arrangement serves further to prevent therelease of gases from the sleeve 37.

'Ihere are other advantages inherent in the plunger construction which has been described. The inner sleeve 38 being made of glass or other refractory material gives additional buoyancy to the plunger, and this is particularly desirable in a front contact switch.

The means for holding the inner and outer sleeves in xed relation to one another produces Ano strain in the parts, and the difference in coefcients of expansion is unimportant. Heretofore, when glass sleeves have been cemented to magnetic sleeves, the heating eiect of the arc necessarily produces a strain due to the difference in coefficients -of expansion and oftentimes, the union of the two materials is disturbed. This cannot happen when the plunger is constructed in the manner taught by this invention.

Since the cement which is commonly used for uniting ceramic material to iron contains certain substances which are deleterious in a switch, there is a decided advantage in employing a construction which obviates the necessity of its use.

A further advantage is found in the fact that the springs 39 and 40 are not allowed to come in contact with the side walls of the envelope and gas pockets between the springs and the envelope are eliminated, as well as friction.

Obviously, the plunger may be modified and changed in detail in many ways without sacricing the full advantages of the preferred form. For example, the top of the glasstube 38 may be provided with a flange 51, as shown in Fig. 5 so that the lower spring 40 alone secures the two sleeves together. The upper spring, then, would merely ride upon the top of the plunger.

Also itis possible for some of the advantages of this invention to be retained by making the outer sleeve of glass or similar material and the inner sleeve of magnetic material. In such an arrangement, the magnetic material would be subjected `to *he action of an electric arc, assuming that the electrode is on the inside of the plunger, and for this reason would be less desirable.

'I'he invention is also applicable to time delay switches of the type shown in Figs. 6 and 7. The structure of the switch shown in these two figures is identical in all respects to the switch shown in Figs. 1 and 2 with the exception that a porous ceramic thimble 52 is substituted for the glass sleeve 38. In this type of switch, as soon as the relay coil is energized, the plunger, here designated 53, is drawn downwardly to .the position shown in Fig. 7 but due to the enrises to a level substantially above the top of the electrode. As the gas pressures on the inside and outside of the thimble are equalized, the mercury levels also equalize so that after a given period of time, depending upon the density of the ceramic material, the mercury will take the position shown in Fig. 7 and the circuit will bev established between the two electrodes.y

In a similar manner, when the relay coil is deenergized, the plunger will rise to a point slightyly below the position of the plunger shown in Fig. 6 carrying with it a column of mercury on the inside and as gas enters the interior of the thimble, due to unequal gas pressure, the mercury level recedes below the bared portion of the central electrode, while at the same time the plunger rises to the position shown in Fig. 6. When the plunger is in this position, the mercury levels on the inside and outside of the plunger have been equalized.

The invention is susceptible of many modiiications within the scope of the appended claims.

What I claim. therefore, is: 1. In a mercury switch, a vertical switch envelope, spaced electrodes sealed through the envelope, a quantity of mercury in the envelope adapted to make or break an electrical circuit through the electrodes according to its level. and a displacer for changing the mercury level comprising telescoping magnetic and refractory members,'one of which projects beyond the other, and means for holding the members in xed relation, said means including a helical spring iitted over the end of the projecting member.

2. In a mercury switch, a vertical switch envelope, spaced electrodes sealed through the envelope, a quantity of mercury in the envelope through the electrodes according to its level, and.

a displacer for changing the mercury level comprising loosely telescoping magnetic and refractory members one of which projects beyond the other, and means for holding the members in fixed relation, said means including a helical spring tted over the end of the projecting member and abutting the end of the other member.

4. In a mercury switch, a vertical switch Aenvel0pe, spaced electrodes sealed throughthe envelope, a quantity of mercury in the envelope adapted'to make or break an electrical circuit through the electrodes according to its level, and a displacer for changing the mercury level, said displacer having an outside diameter slightly less than the inside diameter of the venvelope and comprising telescoping sleeves of magnetic and refractory material, the inner one of which projects beyond the outer one, and means for holding the sleeves in xed relation, said means in- A'cluding a. helical spring tted over the project- -ing end of the inner sleeve.

5. In a mercury switch, a vertical switch lenvelope, spaced electrodes in the envelope, one of which is substantially axially located, a quantity of mercury in the envelope adapted to make or Aportion extending below the 6. A displacer for use in mercury switches comprising telescoping magnetic and refractory membe one of which projects beyond the other, and means for holding the members in xed relation, said means including a helical spring fitted over the end of the projecting member.

7. A displacer for use in mercury switches comprising loosely telescoping magnetic and refractory members one of which projects beyond the other, and means for holding the members in fixed relation, said means including a helical spring tted over the end of the projecting member and abutting the end of the vother member.

8., In a mercury switch, a vertical switch envelope, a pair of upstanding spaced electrodes in the envelope, one of which is substantially axially located and is surrounded by an insulating sleevevto a point adjacent the top of the electrode, a quantity of mercury in the envelope adapted to make or' break an electrical circuit through the electrodes according to its. level, a displacer telescoped over the axial electrode for changing the mercury level, said displacer comprising an outer sleeve of magnetic material, and an inner sleeve of refractory material, the Vbared end of said axial electrode being bent over to one side with a portion extending below the top of the insulating sleeve whereby the insulating sleeve is protected from the ravages of the electric arc which tends to form when the electrical circuit is being opened and closed. 9. In a mercury switch, a vertical switch enthe envelope, one of which is substantially axially located and is surrounded by an insulating sleeve to a point adjacent the top of the electrode, a quantity of mercury in the envelope adapted to make or break an electrical circuit through `the electrodes according to its level, a displacer telescoped over the axial electrode for changing the mercury level, the bared end of said axial elec-A trode being bent over to one side with a portion extending below lthe top of the insulating sleeve whereby the insulating sleeve is protected from the ravages of the electric arc which tends to form when the electrical circuit is being openedl and closed.\

l0. In a mercury switch, a vertical switch en.

velope, spaced electrodes in the envelope, a mercuryV fill, a displacer for changing the mercury level, one of said electrodes being insulated to a point adjacent the top of the electrode and having its bared end bent over to one side with a top of the insulation. I

11. In a mercury switch, a vertical switch envelope, spaced electrodes in the envelope, a mercury fill, and a. displacer for changing'the mercury level, said displacer including telescoping sleevesl of magnetic and refractory material, and a helical spring for holding the sleeves in xed relation. Y

12. In a' mercury switch, a vertical switch en` velope, spaced electrodes in the envelope, a mercury fill, and a. displacer for changing the mercury level, said displacer including telescoping velope, a pair of upstanding spaced electrodes in sleeves of magnetic and refractory material, and a helical spring for holding the sleeves in xed relation, said spring projecting beyond the end of the displacer to cushion the displacer when moved to impact with the end of the envelope.

13. In a mercury switch, a vertical switch envelope, spaced electrodes in the envelope, a mercury `fill, a displacer for changing the mercury level, one of said electrodes being insulated to a point adjacent the top of the electrode and having a portion of its baredvend extending below the top of the insulation.

14. In a mercury switch, a. vertical switch envelope, spaced electrodes in the envelope, a mercury ll', and a displacer for changing the mercury level, said displacer including telescoping sleeves of magnetic and refractory material, the inner sleeve projecting beyond the other, and a 16. In a mercury switch, a verticalswitch en velope, spaced electrodes in the envelope, a mercury ll, a displacer for changing the mercury level, one of said electrodes being insulated to a point above the low level of the mercury and having its bared end extended below the top of the insulation.

CARL H. LARSON. 

